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Linear Function (linear + function)
Kinds of Linear Function Selected AbstractsFruit physical, chemical and aromatic attributes of early, intermediate and late apricot cultivarsJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 6 2010Riccardo Lo Bianco Abstract BACKGROUND: In order to reach good fruit quality, apricots require a balance of sugars and acids as well as a strong apricot aroma. In this study, fruit quality of early, intermediate and late apricot cultivars was evaluated by measuring physical, chemical and olfactory attributes. Multivariate analysis of quality and aroma attributes was used to identify groups of similar cultivars and association with ripening season. RESULTS: Physical, chemical and aromatic attributes showed great variation among cultivars but no relation to ripening season. Aromatic profiles (34 volatiles) of fruit tissues indicated qualitative and quantitative differences among cultivars. Ninfa and Mandorlon were richest in aroma, with a prevailing fruity component; Goldrich and Orange Red were also highly aromatic, with all odour components well represented; Pinkot, Alba and Pellecchiella were lowest in aroma, with a prevailing grassy component. Linear functions including five volatiles (concentrations) and fruit diameter or six aromatic compounds (odour units) and peel colour were found to discriminate cultivars by ripening season. Principal component analysis individuated three groups of cultivars: Ninfa and Mandorlon with sweet and fruity-flavoured fruits; Bulida, Alba, Goldrich, Ouardy and Silvercot with large, acidic and well-coloured fruits; and Fracasso, Pellecchiella, Palummella and Pinkot with small and floral/grassy-flavoured fruits. CONCLUSION: In apricot, detailed analysis of the aromatic profile may represent an efficient tool for classification of genotypes by ripening season, and volatiles with relevant odour contribution may serve as quality markers for selecting towards an extended ripening season of best quality apricots. Copyright © 2010 Society of Chemical Industry [source] Application of the New Keystone-Species Concept to Prairie Dogs: How Well Does It Work?CONSERVATION BIOLOGY, Issue 6 2000Natasha B. Kotliar This prompted Power et al. (1996) to refine the definition: keystone species have large effects on community structure or ecosystem function (i.e., high overall importance), and this effect should be large relative to abundance (i.e., high community importance). Using prairie dogs (Cynomys spp.) as an example, I review operational and conceptual difficulties encountered in applying this definition. As applied to prairie dogs, the implicit assumption that overall importance is a linear function of abundance is invalid. In addition, community importance is sensitive to abundance levels, the definition of community, and sampling scale. These problems arise largely from the equation for community importance, as used in conjunction with removal experiments at single abundance levels. I suggest that we shift from the current emphasis on the dualism between keystone and nonkeystone species and instead examine how overall and community importance vary (1) with abundance, (2) across spatial and temporal scales, and (3) under diverse ecological conditions. In addition, I propose that a third criterion be incorporated into the definition: keystone species perform roles not performed by other species or processes. Examination of how these factors vary among populations of keystone species should help identify the factors contributing to, or limiting, keystone-level functions, thereby increasing the usefulness of the keystone-species concept in ecology and conservation. Although the quantitative framework of Power et al. falls short of being fully operational, my conceptual guidelines may improve the usefulness of the keystone-species concept. Careful attention to the factors that limit keystone function will help avoid misplaced emphasis on keystone species at the expense of other species. Resumen: Se ha sugerido que el concepto de especie pilar no sea usado más en ecología y conservación, principalmente debido a que el concepto ha sido pobremente definido. Esto instigó a Power et al. (1996) a refinar la definición: las especies pilar tienen grandes efectos en la estructura de una comunidad o la función de un ecosistema (alta importancia en lo general), y este efecto debe ser grande en relación con la abundancia (alta importancia en la comunidad). Usando los perros de pradera (Cynomys spp) como ejemplo, revisé las dificultades operativas y conceptuales encontradas durante la aplicación de esta definición. Al aplicarse a perros de pradera, la suposición implícita de que la importancia en lo general es una función lineal de la abundancia es inválida. Además, la importancia en la comunidad es sensible a los niveles de abundancia, a la definición de comunidad y a la escala de muestreo. Estos problemas surgen, en gran medida, de la ecuación para la importancia en la comunidad, al ser usada conjuntamente con experimentos de remoción a un solo nivel de abundancia. Sugiero que el énfasis actual en la dualidad sobre especies pilares/no pilares cambie para examinar cómo varía la importancia en lo general y en la comunidad; (1) con la abundancia, (2) a lo largo de escalas espaciales y temporales, y (3) bajo diversas condiciones ecológicas. Además, propongo que sea incorporado un tercer criterio en la definición: las especies pilar llevan a cabo funciones no llevadas a cabo por otras especies o procesos. El análisis de cómo varían estos factores entre poblaciones de especies pilar ayudará a identificar los factores que contribuyen, o limitan las funciones a nivel pilar, incrementando con ello la utilidad del concepto de especie pilar en ecología y conservación. Aunque el marco de trabajo cuantitativo de Power et al. no llega a ser completamente operacional, mis guías conceptuales pueden mejorar la utilidad de este concepto. Una atención especial a los factores que limitan el funcionamiento pilar ayudaría a evitar un énfasis mal ubicado en especies pilar a costa de otras especies. [source] Predicting the number of ecologically harmful exotic species in an aquatic systemDIVERSITY AND DISTRIBUTIONS, Issue 2 2008Anthony Ricciardi ABSTRACT Most introduced species apparently have little impact on native biodiversity, but the proliferation of human vectors that transport species worldwide increases the probability of a region being affected by high-impact invaders , i.e. those that cause severe declines in native species populations. Our study determined whether the number of high-impact invaders can be predicted from the total number of invaders in an area, after controlling for species,area effects. These two variables are positively correlated in a set of 16 invaded freshwater and marine systems from around the world. The relationship is a simple linear function; there is no evidence of synergistic or antagonistic effects of invaders across systems. A similar relationship is found for introduced freshwater fishes across 149 regions. In both data sets, high-impact invaders comprise approximately 10% of the total number of invaders. Although the mechanism driving this correlation is likely a sampling effect, it is not simply the proportional sampling of a constant number of repeat-offenders; in most cases, an invader is not reported to have strong impacts on native species in the majority of regions it invades. These findings link vector activity and the negative impacts of introduced species on biodiversity, and thus justify management efforts to reduce invasion rates even where numerous invasions have already occurred. [source] An improved validated ultra high pressure liquid chromatography method for separation of tacrolimus impurities and its tautomersDRUG TESTING AND ANALYSIS, Issue 3 2010Acharya Subasranjan Abstract A selective, specific and sensitive ultra high pressure liquid chromatography (UHPLC) method was developed for determination of tacrolimus degradation products and tautomers in the preparation of pharmaceuticals. The chromatographic separation was performed on Waters ACQUITY UPLC system and BEH C8 column using gradient elution of mobile phase A (90:10 v/v of 0.1% v/v triflouroacetic acid solution and Acetonitrile) and mobile phase B (90:10 v/v acetonitrile and water) at a flow rate of 0.6 mL min,1. Ultraviolet detection was performed at 210 nm. Tacrolimus, tautomers and impurities were chromatographed with a total run time of 25 min. Calibration showed that the response of impurity was a linear function of concentration over the range 0.3,6 µg mL,1 (r2 , 0.999) and the method was validated over this range for precision, intermediate precision, accuracy, linearity and specificity. For precision study, percentage relative standard deviation of each impurity was < 15% (n = 6). The method was found to be precise, accurate, linear and specific. The proposed method was successfully employed for estimation of tacrolimus impurities in pharmaceutical preparations. Copyright © 2010 John Wiley & Sons, Ltd. [source] Modelling the hysteresis in the velocity pattern of slow-moving earth flows: the role of excess pore pressureEARTH SURFACE PROCESSES AND LANDFORMS, Issue 4 2005T. W. J. van Asch Abstract This paper describes the velocity pattern of a slow-moving earth flow containing a viscous shear band and a more or less rigid landslide body on top. In the case of small groundwater fluctuations, Bingham's law may describe the velocity of these slow-moving landslides, with velocity as a linear function of excess shear stress. Many authors have stated that in most cases a non-linear version of Bingham's law best describes the moving pattern of these earth flows. However, such an exponential relationship fails to describe the hysteresis loop of the velocity, which was found by some authors. These authors showed that the velocity of the investigated earth flows proved to be higher during the rising limb of the groundwater than during the falling limb. To explain the hysteris loop in the velocity pattern, this paper considers the role of excess pore pressure in the rheological behaviour of earth flows by means of a mechanistic model. It describes changes in lateral internal stresses due to a change in the velocity of the earth flow, which generates excess pore pressure followed by pore pressure dissipation. Model results are compared with a hysteresis in the velocity pattern, which was measured on the Valette landslide complex (French Alps). Copyright © 2005 John Wiley & Sons, Ltd. [source] Diadegma mollipla parasitizing Plutella xylostella: host instar preference and suitabilityENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 1 2008Robert S. Nofemela Abstract Oviposition decisions (i.e., host selection and sex allocation) of female parasitoids are expected to correspond with host quality, as their offspring fitness is dependent on the amount and quality of resources provided by a single host. The host size model assumes that host quality is a linear function of host size, with larger hosts believed to contain a greater quantity of resources, and thus be more profitable than smaller hosts. We tested this assertion in the laboratory on a solitary larval,pupal parasitoid Diadegma mollipla (Holmgren) (Hymenoptera: Ichneumonidae) developing on three instars (second,fourth) of one of its hosts, the diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae). In a no-choice test, parasitism levels and sex ratio (i.e., proportion of female progeny) were significantly high in hosts attacked in the second instar followed by third then fourth instars. However, the few parasitoids that completed a generation from the fourth instars did so significantly faster than conspecifics that started development in the other two instars. In direct observations, however, the parasitoids (i) randomly attacked the various host instars, (ii) spent a similar period examining the various host instars with their ovipositors, (iii) subdued all three host instars with about the same effort, and (iv) no statistical differences were observed in the attack rates on the three host instars. In a choice test, the females parasitized significantly more third instars followed by second then fourth instars. However, total parasitism in this experiment was 43% lower compared to parasitism of only second instars in the no-choice test. No significant differences were detected in progeny sex ratios. In both choice and no-choice tests, significantly more fourth instars died during the course of the experiments than second instars, while third instars were intermediate. The higher parasitism of third than second instars in the choice test indicates that the females perceived larger hosts as higher quality than smaller hosts, despite their lower suitability for larval development. [source] A modeling approach to link food availability, growth, emergence, and reproduction for the midge Chironomus ripariusENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 11 2002Alexandre R. R. Péry Abstract We present models to link feeding with growth, emergence, and reproduction of the midge Chironomus riparius. These models are based on assumptions about the biology of this species and distinguish between males and females. The assumptions are the isomorphism of the chironomidae, the fact that much more energy is used for growth than for maintenance, and the existence of a maximum length for male and female larvae that does not depend on food availability. We supported our assumptions by experimental data and estimated the parameters of the model. We then successfully predicted the length pattern of 2-d-old larvae exposed in an artificial sediment to different feeding levels with different starting densities and also linked emergence time and growth pattern. We found our model to be consistent with data from another study and another species (Chironomus plumosus). As for reproduction, the mean number of eggs per mass was described as a linear function of feeding quantity. Our models could be used in sediment risk assessment to choose feeding level, to build effects models, or to predict the effects of toxicants at the population level. [source] Age,environment model for breast cancerENVIRONMETRICS, Issue 3 2004Nobutane Hanayama Abstract In the field of breast cancer study, it has become accepted that crucial exposures to environmental risks might have occurred years before a malignant tumor is evident in human breasts, while age factors such as ages at menstruation have been known as risks for the disease already. To project trends in two such kinds of risks for the disease, the concept of environment effects is introduced for (age, period)-specific breast cancer mortality rates. Also, a new model, named the age,environment (AE) model, which assumes that the logarithm of the expected rate is a linear function of environment effects and age effects, is proposed. It is shown that, although environment effects have different meanings from period effects or cohort effects, in the age,period,cohort (APC) model, the range space of the design matrix for the AE model is included in that for APC model. It is seen, however, that the AE model provides a better fit to the data for females in Japan and the four Nordic countries than does the APC model in terms of AIC. From the results of ML estimation of the parameters in the AE model based on the data obtained in Japan, we see high levels of environment effects associated with the Sino,Japanese war, World War II and the environmental pollution due to the economy in the recovery period from the defeat. Besides, from those based on the data obtained in the four Nordic countries, we see high levels of environment effects associated with the environment becoming worse after the year of Helsinki Olympics and low levels of them associated with the period including the year of ,Miracle of the Winter War' in Finland. Copyright © 2004 John Wiley & Sons, Ltd. [source] Study of the space,time effects in the concentration of airborne pollutants in the Metropolitan Region of Rio de JaneiroENVIRONMETRICS, Issue 4 2003Marina Silva Paez Abstract In this article, we present an application of models with temporal and spatial components, from the Bayesian point of view, on data pollutants collected in 16 different monitoring sites located in the Metropolitan Area of Rio de Janeiro during 1999. All the models considered here assume conditionally independent observations, with a mean specified by the sum of random temporal and spatial components and a linear function of the maximum daily temperature and indicators of the day of the week. Our aim here is to analyze distinct specifications for the components, assuming different kinds of modeling that are not usually compared. The comparison is based on the posterior predictive loss function proposed by Gelfand and Ghosh (1998). The best specifications for the spatial component were the ones which considered a geostatistical approach to its correlation function. The best specification for the temporal component was the stationary autoregressive form. The pollutant concentrations were interpolated in a grid of points in the area of higher population density at a fixed period of time for the selected model. Copyright © 2003 John Wiley & Sons, Ltd. [source] Institutional change and stability in postcommunist countries, 1990,2002EUROPEAN JOURNAL OF POLITICAL RESEARCH, Issue 4 2008KLAUS ARMINGEON The authors show that institutional change after the institutionalization of the postcommunist regime is limited and lock-in effects are strong. This applies to the more democratic and affluent countries as well as to the more authoritarian regimes. The authors do not find evidence for theories of institutional change that see institutional development as a linear function of socio-economic factors such as affluence or of domestic political power distribution. The European Union and NATO have an effect that is limited to the overall democratic character of the system. [source] Determining soil saturated hydraulic conductivity and sorptivity from single ring infiltration testsEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 1 2007J. Touma Summary The difference between the cumulative infiltration occurring during three-dimensional axisymmetric and one-dimensional vertical flow is a linear function of time. The slope of this line is a function of the source radius, initial and final volumetric soil water contents and the soil sorptivity. This allows the determination of the sorptivity and saturated conductivity of the soil from data of axisymmetric flow in a single ring of small diameter under negligible head of water. The method is based on the optimization of the sorptivity and saturated conductivity on the one-dimensional vertical cumulative infiltration inferred from axisymmetric flow data. To examine the reliability of the method to determine these parameters, numerical three- and one-dimensional data are generated on soils with known hydrologic properties from the literature. The linearity versus time of the difference of the two types of flow is verified. Several physically based expressions for the vertical cumulative infiltration as a function of time are considered. The optimized values of the sorptivity and saturated conductivity are compared to the their real known values. Despite the large errors on the optimized parameters, namely the saturated conductivity, the error on the vertical predicted cumulative infiltration is limited to 10%. This makes possible the application of this method on a large scale for hydrological modelling purposes. [source] Inflorescence characteristics, seed composition, and allometric relationships predicting seed yields in the biomass crop Cynara cardunculusGCB BIOENERGY, Issue 3 2010S. V. ARCHONTOULIS Abstract Cynara (Cynara cardunculus) is a perennial C3 herb that has its potential as bioenergy crop. This paper aims (a) to derive empirical relationships to predict cynara seed yield per head and per unit area, avoiding laborious extraction of seeds from the complex structure of its inflorescences; (b) to determine the head-weight distribution per unit area, the seed composition and the oil profile of cynara seeds; and (c) to estimate the range of cynara biomass, seed and oil yield in representative parts of Greece. We analyzed 16 field experiments, varying in crop age and environmental conditions in Greece. Seed yield per head (SYhead) can be accurately predicted as a linear function of dry head weight (Hw): SYhead=0.429·Hw,2.9 (r2=0.96; n=617). Based on this relationship, we developed a simple two-parameter equation to predict seed yield per unit area (SY): SY=HN·(0.429·,,2.9), where , is the mean head weight (g head,1) and HN is the total number of heads per unit area, respectively. The models were tested against current and published data (n=180 for head-level; n=35 for unit area-level models), and proved to be valid under diverse management and environmental conditions. Attainable cynara seed yields ranged from 190 to 480 g m,2 yr,1, on dry soils and on aquic soils (shallow ground water level). This variation in seed yield was sufficiently explained by the analyses of head-weight distribution per unit area (small, medium and large heads) and variability of seed/head weight ratio at head level. Seed oil concentration (average: 23%) and crude protein concentration (average: 18.7%) were rather invariant across different seed sizes (range: 26,56 mg seed,1) and growing environments. [source] Determining the dilation factor in 4D monitoring of compacting reservoirs by rock-physics modelsGEOPHYSICAL PROSPECTING, Issue 6 2007José M. Carcione ABSTRACT Hydrocarbon depletion and fluid injection cause compaction and stretching of the reservoir and overburden layers. 4D prestack seismic data can be used to detect these changes because compaction/stretching causes changes in traveltimes and seismic velocities. We show that, by using two different petro-elastic models at varying effective pressures, a good approximation is to assume that the fractional changes in layer thickness, ,L/L, and seismic velocity, ,v/v, are related by a linear function of ,L/L. The slope of this function (the dilation factor, ,= (,v/v)/(,L/L)) is negative and its absolute value generally decreases (shale, low porosity) or increases (sandstone, high porosity) with increasing layer thickness and decreasing effective pressure. The analysis is mainly performed for isotropic deformations. The dilation factor for uniaxial deformations is smaller in absolute value. The dilation factor, which can be calculated from time-lapse data, can be used to predict reservoir compaction/stretching as a function of depth and surface subsidence. [source] Modeling of a Deep-Seated Geothermal System Near Tianjin, ChinaGROUND WATER, Issue 3 2001Zhou Xun A geothermal field is located in deep-seated basement aquifers in the northeastern part of the North China Plain near Tianjin, China. Carbonate rocks of Ordovician and Middle and Upper Proterozoic age on the Cangxian Uplift are capable of yielding 960 to 4200 m3/d of 57°C to 96°C water to wells from a depth of more than 1000 m. A three-dimensional nonisothermal numerical model was used to simulate and predict the spatial and temporal evolution of pressure and temperature in the geothermal system. The density of the geothermal water, which appears in the governing equations, can be expressed as a linear function of pressure, temperature, and total dissolved solids. A term describing the exchange of heat between water and rock is incorporated in the governing heat transport equation. Conductive heat flow from surrounding formations can be considered among the boundary conditions. Recent data of geothermal water production from the system were used for a first calibration of the numerical model. The calibrated model was used to predict the future changes in pressure and temperature of the geothermal water caused by two pumping schemes. The modeling results indicate that both pressure and temperature have a tendency to decrease with time and pumping. The current withdrawal rates and a pumping period of five months followed by a shut-off period of seven months are helpful in minimizing the degradation of the geothermal resource potential in the area. [source] Lesions of the mammillary body region alter hippocampal movement signals and theta frequency: Implications for path integration modelsHIPPOCAMPUS, Issue 9 2008Patricia E. Sharp Abstract Cells throughout the hippocampal formation are involved in processing spatial information. These same cells also show an influence of locomotor activity, and these movement signals are thought to be critical for the path integration abilities of these cells. Nuclei in the mammillary region provide ascending influences to the hippocampal formation and have been implicated in influencing both hippocampal spatial and theta signals. Here, we report the effects of mammillary lesions on movement-related signals in several hippocampal subregions. We find first, as predicted by earlier work, these lesions cause an approximately 1 Hz reduction in the frequency of theta modulation of cell firing. According to recent theoretical work, this might, in turn, be expected to influence the size of hippocampal place fields. Our data do not confirm this prediction for any of the hippocampal regions examined. Second, we report lesion effects on the relationship between firing rate and running speed for the hippocampal cells. These lesions caused a reduction in both the slope and intercept of rate-by-speed functions for cells in the hippocampus and postsubiculum. Surprisingly, cells in subiculum showed an opposite effect, so that the excitatory influence of locomotion was enhanced. Path integration theories predict that the speed at which path integration occurs is related to the strength of this movement signal. In remarkable accordance with this prediction, we report that the timing of the place cell signals is slowed following mammillary lesions for hippocampal and postsubicular cells, but, in contrast, is speeded up for subicular cells. In fact, the timing for place signals across lesion condition and brain region is predicted by a single linear function which relates timing to the strength of the running speed signal. Thus, these data provide remarkable support for some aspects of current path integration theory, while posing a challenge for other aspects of these same theories. © 2008 Wiley-Liss, Inc. [source] A development of the discontinuous deformation analysis for rock fall analysisINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 10 2005Jian-Hong Wu Abstract Discontinuous deformation analysis (DDA), a discrete numerical analysis method, is used to simulate the behaviour of falling rock by applying a linear displacement function in the computations. However, when a block rotates, this linear function causes a change in block size called the free expansion phenomenon. In addition, this free expansion results in contact identification problems when the rotating blocks are close to each other. To solve this problem of misjudgment and to obtain a more precise simulation of the falling rock, a new method called Post-Contact Adjustment Method has been developed and applied to the program. The basic procedure of this new method can be divided into three stages: using the linear displacement function to generate the global matrix, introducing the non-linear displacement function to the contact identification, and applying it to update the co-ordinates of block vertices. This new method can be easily applied to the original DDA program, demonstrating better contact identification and size conservation results for falling rock problems than the original program. Copyright © 2005 John Wiley & Sons, Ltd. [source] Adaptive backstepping control for a class of time delay systems with nonlinear perturbationsINTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 3 2008Chang-Chun Hua Abstract The sliding mode control method has been extensively employed to stabilize time delay systems with nonlinear perturbations. Although the resulting closed-loop systems have good transient and steady-state performances, the designed controllers are dependent on the time delays. But one knows that it is difficult to obtain the precise delay time in practical systems, especially when it is time varying. In this paper, we revisit the problem and use the backstepping method to construct the state feedback controller. First, a coordinate transformation is used to obtain a cascade time delay system. Then, a linear virtual control law is designed for the first subsystem. The memoryless controller is further constructed based on adaptive method for the second subsystem with the uncertainties bounded by linear function. By choosing new Lyapunov,Krasovskii functional, we show that the system state converges to zero asymptotically. Via the proposed approach, we also discuss the case that the uncertainties are bounded by nonlinear functions. Finally, simulations are done to verify the effectiveness of the main results obtained. Copyright © 2007 John Wiley & Sons, Ltd. [source] A linearly adaptive gate drive technique for light-load efficiency improvement of DC,DC convertersINTERNATIONAL JOURNAL OF CIRCUIT THEORY AND APPLICATIONS, Issue 10 2009Pang-Jung Liu Abstract This paper presents a linearly adaptive gate drive technique to improve the light-load efficiency of DC,DC converters. The optimal-driving voltages of the power MOSFETs for reducing gate-driving loss can be well modeled by a linear function of the load current. By scaling the gate drive voltage dynamically with respect to load current, the light-load efficiency can be enhanced. The experimental result shows that the proposed gate drive technique can attain about 9% incremental light-load efficiency enhancement. Copyright © 2008 John Wiley & Sons, Ltd. [source] A tree-based approach to matchmaking algorithms for resource discoveryINTERNATIONAL JOURNAL OF NETWORK MANAGEMENT, Issue 5 2008Md. Rafiqul Islam One of the essential operations in a distributed computing is resource discovery. A resource discovery service provides mechanisms to identify the set of resources capable of satisfying the requirements of a job from a large collection of resources. The matchmaking framework provides a reasonable solution to resource management in a distributed environment; it is composed of four important components as classified advertisement (classad), matchmaker protocol, matchmaking algorithm and claiming protocols. Most of the time required to find a resource depends on the performance of the matchmaking algorithms. A distributed environment introduces a large set of heterogeneous resources which is always changing. The matchmaking algorithms should incorporate with this highly changing environment. In this paper we proposed a fast and efficient searching method for matchmaking algorithms which also deals with resource heterogeneity. The proposed approach reduces the searching time to a linear function from a cubic function proposed by R. Raman, M. Livny, and M. Solomon. We discuss briefly the working principles of the method and compare the experimental results of the proposed matchmaking algorithm with those of the existing algorithm. Copyright © 2008 John Wiley & Sons, Ltd. [source] On Wiener-type polynomials of thorn graphsJOURNAL OF CHEMOMETRICS, Issue 12 2009Bo Zhou Abstract We derive the expressions of the ordinary, the vertex-weighted and the doubly vertex-weighted Wiener polynomials of a type of thorn graph, for which the number of pendant edges attached to any vertex of the underlying parent graph is a linear function of its degree. We also define variable vertex-weighted Wiener polynomials and calculate them for the same type of thorn graphs. Copyright © 2009 John Wiley & Sons, Ltd. [source] Soft energy function and generic evolutionary method for discriminating native from nonnative protein conformationsJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 9 2008Yi-yuan Chiu Abstract We have developed a soft energy function, termed GEMSCORE, for the protein structure prediction, which is one of emergent issues in the computational biology. The GEMSORE consists of the van der Waals, the hydrogen-bonding potential and the solvent potential with 12 parameters which are optimized by using a generic evolutionary method. The GEMSCORE is able to successfully identify 86 native proteins among 96 target proteins on six decoy sets from more 70,000 near-native structures. For these six benchmark datasets, the predictive performance of the GEMSCORE, based on native structure ranking and Z -scores, was superior to eight other energy functions. Our method is based solely on a simple and linear function and thus is considerably faster than other methods that rely on the additional complex calculations. In addition, the GEMSCORE recognized 17 and 2 native structures as the first and the second rank, respectively, among 21 targets in CASP6 (Critical Assessment of Techniques for Protein Structure Prediction). These results suggest that the GEMSCORE is fast and performs well to discriminate between native and nonnative structures from thousands of protein structure candidates. We believe that GEMSCORE is robust and should be a useful energy function for the protein structure prediction. © 2008 Wiley Periodicals, Inc. J Comput Chem 2008 [source] How can self-regulated learning be supported in mathematical E-learning environments?JOURNAL OF COMPUTER ASSISTED LEARNING, Issue 1 2006B. Kramarski Abstract This study compares two E-learning environments: E-learning supported with IMPROVE self-metacognitive questioning (EL+IMP), and E-learning without explicit support of self-regulation (EL). The effects were compared between mathematical problem-solving and self-regulated learning (SRL). Participants were 65 ninth-grade students who studied linear function in Israeli junior high schools. Results showed that EL+IMP students significantly outperformed the EL students in problem-solving procedural and transfer tasks regarding mathematical explanations. We also found that the EL+IMP students outperformed their counterparts in using self-monitoring strategies during problem solving. This study discusses both the practical and theoretical implications of supporting SRL in mathematical E-learning environments. [source] Determining the causality between retail price and consumer demand in a linear function when demand-shift variables are missing but wholesale prices are availableAGRIBUSINESS : AN INTERNATIONAL JOURNAL, Issue 2 2005W. Erno Kuiper A test procedure is proposed to test for the simultaneous nature of the relationship between price and quantity with respect to consumer demand of fresh products at the level of an individual retail chain. It is argued in the literature that, on the sector level, inverse demand systems in which quantities are exogenous and prices are the dependent variables are better able to describe consumer demand behavior in case of perishable products whose quantities may be treated as fully price inelastic in the short run. Nevertheless, applying our test procedure to six fresh vegetable products sold by a Dutch supermarket chain reveals that consumer demand for fresh products is better described by a simultaneous price,quantity relationship. [EconLit citations: C320, D420, Q110.] © 2005 Wiley Periodicals, Inc. Agribusiness 21: 167,176, 2005. [source] On the nature of modified composite electrical effect parametersJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 10 2003Marvin Charton Abstract It is shown that a correlation of some property, reactivity or biological activity with pure parameters can also be carried out with composite parameters to produce a model with comparable statistics. Modified composite electrical effect parameters can be obtained from known composite electrical effect parameters by means of an algorithm such as ,X,,=,(,X + c)m in which ,X, is the modified composite electrical effect parameter (MCEEP), ,X the original composite electrical effect parameter, c a constant and m an exponent. MCEEPs were calculated from this equation with c equal to 2 and m ranging from ,4 to 4 when ,X is ,m or ,p, and from ,2 to 2 when it is ,p+. They were used to model 10 sets of chemical reactivities that had previously been correlated with the pure parameters ,1, ,d and ,e, which represent the localized (field), intrinsic delocalized (resonance) and electronic demand sensitivity electrical effects, respectively. In most cases both the pure and the modified composite parameters give comparable fits to the data as measured by the values of 100R2, in accord with the prediction. The composition of the MCEEPs was a linear function of m. The advantage in using pure parameters is that they are readily interpretable. Correlations with composite parameters can be interpreted only if their composition has been determined. These results provide an understanding of the way in which topological parameters work. Copyright © 2003 John Wiley & Sons, Ltd. [source] Functional syndiotactic poly(,-hydroxyalkanoate)s via stereoselective ring-opening copolymerization of rac -,-butyrolactone and rac -allyl-,-butyrolactoneJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 12 2009Noureddine Ajellal Abstract The copolymerization of racemic ,-butyrolactone (rac -BLMe) with racemic "allyl-,-butyrolactone" (rac -BLallyl) in toluene, catalyzed by the discrete amino-alkoxy-bis(phenolate) yttrium-amido complex 1, gave new poly(,-hydroxyalkanoate)s with unsaturated side chains. The poly(BLMe - co -BLallyl) copolymers produced have a highly syndiotactic backbone structure (Pr = 0.80,0.84) with a random enchainment of monomer units, as evidenced by 13C NMR, and high molecular weight (Mn up to 58,000 g mol,1) with a narrow polydispersity (Mw/Mn = 1.07,1.37), as determined by GPC. The comonomer incorporation (5,50 mol % rac -BLallyl) was a linear function of the feed ratio. The pendant vinyl bond of the side-chains in those poly(BLMe - co -BLallyl) copolymers allowed the effective introduction of hydroxy or epoxy groups via dihydroxylation, hydroboration-oxidation or epoxidation reactions. NMR studies indicated that all of these transformations proceed in an essentially quantitative conversion and do not affect the macromolecular architecture. Some thermal properties (Tm, ,Hm, Tg) of the prepared polymers have been also evaluated. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3177,3189, 2009 [source] Using data mining to predict K,12 students' performance on large-scale assessment items related to energyJOURNAL OF RESEARCH IN SCIENCE TEACHING, Issue 5 2008Xiufeng Liu This article reports a study on using data mining to predict K,12 students' competence levels on test items related to energy. Data sources are the 1995 Third International Mathematics and Science Study (TIMSS), 1999 TIMSS-Repeat, 2003 Trend in International Mathematics and Science Study (TIMSS), and the National Assessment of Educational Progress (NAEP). Student population performances, that is, percentages correct, are the object of prediction. Two data mining algorithms, C4.5 and M5, are used to construct a decision tree and a linear function to predict students' performance levels. A combination of factors related to content, context, and cognitive demand of items and to students' grade levels are found to predict student population performances on test items. Cognitive demands have the most significant contribution to the prediction. The decision tree and linear function agree with each other on predictions. We end the article by discussing implications of findings for future science content standard development and energy concept teaching. © 2007 Wiley Periodicals, Inc. J Res Sci Teach 45: 554,573, 2008 [source] Predicting future citation behaviorJOURNAL OF THE AMERICAN SOCIETY FOR INFORMATION SCIENCE AND TECHNOLOGY, Issue 5 2003Quentin L. Burrell In this article we further develop the theory for a stochastic model for the citation process in the presence of obsolescence to predict the future citation pattern of individual papers in a collection. More precisely, we investigate the conditional distribution,and its mean,of the number of citations to a paper after time t, given the number of citations it has received up to time t. In an important parametric case it is shown that the expected number of future citations is a linear function of the current number, this being interpretable as an example of a success-breeds-success phenomenon. [source] Simple linear formulation for magnetostimulation specific to MRI gradient coilsMAGNETIC RESONANCE IN MEDICINE, Issue 5 2001Blaine A. Chronik Abstract A simple linear formulation for magnetostimulation thresholds specific to MRI gradient coils is derived based on established hyperbolic electrostimulation strength vs. duration relations. Thresholds are derived in terms of the gradient excursion required to cause stimulation, and it is demonstrated that the threshold curve is a linear function of the gradient switching time. A parameter , is introduced as being fundamental in the evaluation of gradient coil stimulation. , is a map of the induced electric field per unit gradient slew rate, and can be calculated directly from the gradient coil wire pattern. Consideration of , alone is sufficient to compare stimulation thresholds between different gradient coil designs, as well as to evaluate the expected dependency of stimulation threshold on position within the gradient coil. The linear gradient threshold curve is characterized by two parameters: SRmin and ,Gmin. SRmin is the slope of the threshold curve and represents the minimum slew rate required to cause stimulation in the limit of infinite gradient strength. ,Gmin is the vertical axis intercept of the curve and represents the minimum gradient excursion required to cause stimulation in the limit of infinite slew rate. Both SRmin and ,Gmin are functions of both , and the standard tissue parameters Er (rheobase) and ,c (chronaxie time). The ease with which both the gradient system performance and the stimulation thresholds can be plotted on the same axes is noted and is used to introduce the concept of a piece-wise linear operational limit curve for a gradient system. Magn Reson Med 45:916,919, 2001. © 2001 Wiley-Liss, Inc. [source] Toward faster algorithms for dynamic traffic assignment.NETWORKS: AN INTERNATIONAL JOURNAL, Issue 1 2003Abstract Being first in a three-part series promising a practical solution to the user-equilibrium dynamic traffic assignment problem, this paper devises a parametric quickest-path tree algorithm, whose model makes three practical assumptions: (i) the traversal time of an arc i , j is a piecewise linear function of the arrival time at its i -node; (ii) the traversal time of a path is the sum of its arcs' traversal times; and (iii) the FIFO constraint holds, that is, later departure implies later arrival. The algorithm finds a quickest path, and its associated earliest arrival time, to every node for every desired departure time from the origin. Its parametric approach transforms a min-path tree for one departure-time interval into another for the next adjacent interval, whose shared boundary the algorithm determines on the fly. By building relatively few trees, it provides the topology explicitly and the arrival times implicitly of all min-path trees. Tests show the algorithm running upward of 10 times faster than the conventional brute-force approach, which explicitly builds a min-path tree for every departure time. Besides dynamic traffic assignment, other applications for which these findings have utility include traffic control planning, vehicle routing and scheduling, real-time highway route guidance, etc. © 2002 Wiley Periodicals, Inc. [source] Robust location problems with pos/neg weights on a treeNETWORKS: AN INTERNATIONAL JOURNAL, Issue 2 2001Rainer E. Burkard Abstract In this paper, we consider different aspects of robust 1-median problems on a tree network with uncertain or dynamically changing edge lengths and vertex weights which can also take negative values. The dynamic nature of a parameter is modeled by a linear function of time. A linear algorithm is designed for the absolute dynamic robust 1-median problem on a tree. The dynamic robust deviation 1-median problem on a tree with n vertices is solved in O(n2 ,(n) log n) time, where ,(n) is the inverse Ackermann function. Examples show that both problems do not possess the vertex optimality property. The uncertainty is modeled by given intervals, in which each parameter can take a value randomly. The absolute robust 1-median problem with interval data, where vertex weights might also be negative, can be solved in linear time. The corresponding deviation problem can be solved in O(n2) time. © 2001 John Wiley & Sons, Inc. 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